In many cases, a power converter device is configured as follows. That is, a power converter device comprises two semiconductor device groups comprising a switching element and a freewheeling diode, wherein the switching element and the freewheeling diode are connected in parallel. The two semiconductor device groups are connected in series, a DC voltage is applied to both ends of the semiconductor device groups and an output terminal is provided at a connection point between semiconductor device groups. In the above-mentioned power converter device, when a switching element of an upper arm is an ON-state, a positive DC voltage is outputted to the output terminal, and when a switching element of a lower arm is an ON-state, a negative DC voltage is outputted to the output terminal. Consequently, ON/OFF of a switching element is controlled so as to make an average output voltage of one switching period equal to a voltage command. Ideally, an average output voltage of one switching period is equal to a voltage command. When an IGBT is used as a switching element, a current flows in either of a switching element or a freewheeling diode according to the direction of current. In the above-mentioned power converter device, a voltage drop (on-voltage) is generated in a switching element; therefore an output voltage according to a command value can not be obtained. In Patent Document 1, technology to obtain an output voltage according to a command value is indicated as follows. That is, in order to compensate the voltage drop, a current sensor is provided at an upper arm and a lower arm, respectively, and a current which flows in each arm is judged whether the current flows in a switching element or in a freewheeling diode so as to compensate the each voltage drop.
On the other hand, there is a power converter device which performs a synchronous rectification in which a MOSFET is used as a switching element, and a division current between a switching element and a freewheeling diode is used so as to reduce the loss. (for example, Patent Document 2)